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1.
We tested the effects of generally used chemiluminescence inhibitors on an example of luminol chemiluminescence elicited by xanthine oxidase/hypoxanthine system, and attempted to assess their capabilities in discovering the reaction pathways leading to chemiluminescence. Luminol itself is a xanthine oxidase inhibitor and its concentration affects the reaction mechanism. Maximal chemiluminescence response was observed at luminol concentration inhibiting urate production. Chemiluminescence was totally inhibited by superoxide dismutase, the inhibition by catalase depended on luminol concentration. Ferricytochrome c, a detector of superoxide, either stimulated or inhibited chemiluminescence in a concentration-dependent manner. Chemiluminescence was highly stimulated by peroxidases. A pronounced inhibition of chemiluminescence was caused by chelators; 1 mm desferal and 0.01 mm diethyldithiocarbamate. It is suggested that measurement of luminol chemiluminescence is not a suitable method for discrimination among individual reactive oxygen species and their quantitative determination in biological systems. 相似文献
2.
The effect of light on the rate of ethylene production was monitored using two different techniques—leaf segments incubated in closed flasks versus intact plants in a flow-through open system. Three different plants were used, viz sunflower ( Helianthus annuus), tomato ( Lycopersicon esculentum), and soybean ( Glycine max). Experiments were conducted both in the presence and absence of 1-aminocyclopropane-1-carboxylic acid (ACC). The results obtained indicate that, in all three species studied, light strongly inhibits ethylene production when cut leaf segments are incubated in the presence of ACC in closed flasks. When ethylene measurements are made with ACC-sprayed intact plants using a continuous flow system, the effect of light on ethylene production is only marginal. In leaf segments of sunflower and soybean incubated only in distilled H2O in closed flasks, light promotes ethylene production. In tomato, there is no difference between the rate of ethylene production between light and darkness under such conditions. When measurements are made with intact plants in a continuous flow system, the rate of ethylene production is almost identical in light and darkness, in the three plants studied. It is concluded that the effect of light on cut leaf segments incubated in the presence of ACC in closed flasks can be attributed to the techniques used for these measurements. Light has little effect on ethylene production by intact plants in an open system. 相似文献
3.
Isolated soybean ( Glycine max L. var Hood) embryonic axes have a spontaneous chemiluminescence (about 150 counts per minute per embryo) that increases showing two phases, upon water imbibition. The first photoemission burst was measured between 0 and 7 hours of imbibition with a maximum of about 350 counts per minute per embryo after 2 hours. The second photoemission phase, between 7 and 30 hours, increased from about 220 to 520 counts per minute per embryo. Both chemiluminescence phases were inhibited by infused butylated hydroxyanisole while only the second phase was inhibited by infused salicylhydroxamic acid. On the basis of the sensitivity of the lipoxygenase reaction to both inhibitors (about 90%), the first burst is tentatively assigned to oxy-radicals mobilized upon water uptake by the embryonic axes, and the second phase is tentatively identified as due to lipoxygenase activity. The in vivo lipoxygenase activity of the embryonic axes was estimated by both the fraction of total oxygen uptake that was inhibited by butylated hydroxyanisole and by the fraction of photoemission that was inhibited by butylated hydroxyanisole and by salicylhydroxamic acid. Both approaches indicated marked increases (5-fold and 12-fold, respectively) of lipoxygenase activity between 2 and 30 hours of imbibition. The measured chemiluminescence per O 2 uptake ratio (the experimental quantum yield) for the lipoxygenase reaction (3.3 × 10 −14 counts per O 2 molecule) was used to estimate the O 2 uptake due to lipoxygenase activity from the photoemission of the embryonic axes after 30 hours of imbibition. The value (0.54 microliters per minute per axis) was close to the butylated hydroxyanisole-sensitive O 2 uptake (1.2 microliters O 2 per minute per axis) of the same embryonic axes. Chemiluminescence may afford a noninvasive assay for lipoxygenase activity in intact plant tissues. 相似文献
4.
A comparative H 2O 2-luminol- and Fe(II)-induced chemiluminescence analysis of extracts of two strains of marine oil oxidizing bacteria Actinetobacter calcoaceticus cultivated either in the presence or absence of oil was carried out. Effects of these extracts on E. coli MG1655 biosensor (pSoxS-lux) were studed. Activation of H 2O 2-induced chemiluminescence in the presence of oil was observed. This suggests activation of free radical lipid peroxidation.
Aqueous extracts of microorganisms cultivated in the presence of oil were shown to activate reactive oxygen species production
(ROS) in Fe(II)-induced chemiluminescence reaction mixture. Acetone-ethanol extracts induced antioxidative systems of both
strains. Chemiluminescence analysis in a biological system carried utilizing E. coli MG1655 (pSoxS-lux) revealed that aqueous extracts of the strains cultivated in the absence of oil contained potential antioxidants. 相似文献
5.
Photosynthetic gas exchange in the leaves of wheat plants growing in a nutrient solution containing 0 or 2 mM silicon (Si) and inoculated with Pyricularia oryzae was investigated. The blast severity, the gas exchange parameters such as net carbon assimilation rate ( A), stomatal conductance to water vapor ( g s), internal CO 2 concentration ( C i) and transpiration rate ( E) and the concentration of pigments (chlorophyll a, chlorophyll b and carotenoids) were determined. The blast severity was reduced by 67.66 % on +Si plants compared with the ?Si plants. There were significant increases of 29.3, 17.7 and 45 % for A at 48, 72 and 96 h after inoculation (hai); 26.7 and 49 % for g s at 48 and 96 hai; and 25.2 and 31.4 % for E at 48 and 96 hai, respectively, for +Si inoculated plants when compared with the ?Si inoculated plants. The C i was significantly lower for +Si inoculated plants than for ?Si inoculated plants at 48, 72 and 96 hai. For inoculated plants, the concentrations of chlorophyll a and chlorophyll b were significantly higher for the +Si plants compared with the ?Si plants at 72 and 96 hai. The results of this study clearly demonstrated that the supply of Si to the wheat plants was associated with lower blast severity in parallel with improved gas exchange performance, resulting in higher energy for mounting successful defense strategies against P. oryzae infection. 相似文献
6.
It is not clear if tree canopies in savanna ecosystems exert positive or negative effects on soil moisture, and how these might affect understory plant carbon balance. To address this, we quantified rooting-zone volumetric soil moisture (?? 25?cm), plant size, leaf-level and whole-plant gas exchange of the bunchgrass, bush muhly ( Muhlenbergia porteri), growing under and between mesquite ( Prosopis velutina) in a southwestern US savanna. Across two contrasting monsoon seasons, bare soil ?? 25?cm was 1.0?C2.5% lower in understory than in the intercanopy, and was consistently higher than in soils under grasses, where ?? 25?cm was similar between locations. Understory plants had smaller canopy areas and volumes with larger basal diameters than intercanopy plants. During an above-average monsoon, intercanopy and understory plants had similar seasonal light-saturated leaf-level photosynthesis ( A net-sat), stomatal conductance ( g s-sat), and whole-plant aboveground respiration ( R auto), but with higher whole-plant photosynthesis (GEP plant) and transpiration ( T plant) in intercanopy plants. During a below-average monsoon, intercanopy plants had higher diurnally integrated GEP plant, R auto, and T plant. These findings showed little evidence of strong, direct positive canopy effects to soil moisture and attendant plant performance. Rather, it seems understory conditions foster competitive dominance by drought-tolerant species, and that positive and negative canopy effects on soil moisture and community and ecosystem processes depends on a suite of interacting biotic and abiotic factors. 相似文献
7.
The light- and sulfide-dependent induction process leading to photosystem I-mediated sulfide utilization by Oscillatoria limnetica, for either H 2 evolution or CO 2 photoassimilation, was studied. The identical dependence on pH of the lag length, the inhibition of leucine incorporation and final H 2S concentration imply that the latter exerts a deleterious effect on nonadapted cells. Na-dithionite (Na2S2O4), Na-sulfite (Na2SO3), or ethanol cannot serve as photosynthetic electron donors. However, when these compounds were added to the sulfide-containing system, the need for induction was eliminated. At pH 6.9, in the presence of 3.5 millimolar sulfide, these substances (at concentrations of 10 millimolar, 5 millimolar, or 0.4 molar, respectively) completely abolished the delay preceding sulfide-dependent H2 evolution. It is suggested that all three compounds expose a site capable of directly accepting sulfide electrons. Only dithionite could adapt the cells to sulfide utilization on its own. Sulfite or ethanol acted only in the presence of sulfide. It is implied that this specific activity of dithionite is related to its characteristic low redox potential. Sulfide-dependent H2 evolution was insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, but was inhibited by the plastoquinone antagonist 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, in the presence as well as in the absence of dithionite. In both cases, therefore, the plastoquinone was implied in the electron transport from sulfide. 相似文献
8.
Gas holdup investigations were performed in three concentric-tube airlift reactors of different scales of operation (RIMP: 0.070 m 3; RIS-1: 2.5 m 3; RIS-2: 5.2 m 3; nominal volumes). The influences of the top and bottom clearances and the flow resistances at the downcomer entrance were studied using tap water as liquid phase and air as gaseous phase, at atmospheric pressure. It was found that the gas holdup in the individual zone of the reactor: riser, downcomer and gas-separator, as well as that in the overall reactor is affected by the analyzed geometrical parameters in different ways, depending on their effects on liquid circulation velocity. Gas holdup was satisfactorily correlated with Fr, Ga, bottom spatial ratio ( B), top spatial ratio ( T), gas separation ratio ( Y) and downcomer flow resistance ratio ( A d /A R ). Correlations are presented for gas holdup in riser, downcomer, gas separator and for the total gas holdup in the reactor. All the above stressed the importance of the geometry in dynamic behaviour of airlift reactors. 相似文献
9.
Studies of H 2 evolution by N 2 fixing systems are frequently limited by an inability to accurately measure H 2 gas concentrations of less than about 10 microliters per liter. In this study, a H 2 gas analyzer is described which is able to accurately and reproducibly detect up to 100 times lower H 2 concentrations than most thermal conductivity gas chromatographs or other conventional instruments used for the measurement of H 2 gas. This high level of sensitivity (maximum of about 0.02 microliter per liter H 2 per millivolt output) and the ability to continuously monitor H 2 concentration directly in a flowing gas stream, makes this instrument well suited for use in an open gas exchange system. Since the sensor used in the instrument was also sensitive to other combustible gases, it was necessary to demonstrate that H2 was the only combustible gas produced by the N2 fixing system being studied. When an air stream was passed through a pot containing nodulated soybean (Glycine max L.) roots, gas chromatographic analysis of the effluent gas stream revealed that H2 was the only combustible gas present. These results were supported by other studies in which no combustible gases were detected in the effluent gas stream from soybean roots nodulated with USDA 110, a Rhizobium strain which displays active uptake hydrogenase activity. 相似文献
10.
The effect of light on the dwarfing allele, le, in Pisum sativum L. was tested as the growth response to gibberellins prior to or beyond the presumed block in the gibberellin biosynthetic pathway. The response to the substrate (GA 20), the product (GA 1), and a nonendogenous early precursor (steviol) was compared in plants bearing the normal Le and the deficient lele genotypes in plants made low in gibberellin content genetically ( nana lines) or by paclobutrazol treatment to tall (cv Alaska) and dwarf (cv Progress) peas. Both genotypes responded to GA 1 under red irradiation and in darkness. The lele plants grew in response to GA 20 and steviol in darkness but showed a much smaller response when red irradiated. The Le plants responded to GA 20 and steviol in both light and darkness. The red effects on lele plants were largely reversible by far-red irradiation. It is concluded that the deficiency in 3β-hydroxylation of GA 20 to GA 1 in genotype lele is due to a Pfr-induced blockage in the expression of that activity. 相似文献
11.
The effect of O 2 on the CO 2 exchange of detached leaves of corn ( Zea mays), wheat ( Triticum vulgare), oats ( Avena sativa), barley ( Hordeum vulgare), timothy ( Phleum pratense) and cat-tail ( Typha angustifolia) was measured with a Clark oxygen electrode and infrared carbon dioxide analysers in both open and closed systems. Corn leaves did not produce CO2 in the light at any O2 concentration, as was shown by the zero CO2 compensation point and the absence of a CO2 burst in the first minute of darkness. The rate of photosynthesis was inhibited by O2 and the inhibition was not completely reversible. On the other hand, the steady rate of respiration after a few minutes in the dark was not affected by O2. These results were interpreted as indicating the absence of any measurable respiration during photosynthesis. Twelve different varieties of corn studied all responded to O2 in the same way. The other 5 monocotyledons studied did produce CO2 in the light. Moreover, the CO2 compensation point increased linearly with O2 indicating a stimulation of photorespiration. The implications of the lack of photorespiration in studies of primary productivity are discussed. 相似文献
12.
With an experimental system using mass spectrometry techniques and infra-red gas analysis of CO 2 developed for aquatic plants, we studied the responses to various light intensities and CO 2 concentrations of photosynthesis and O 2 uptake of the red macroalga Chondrus crispus S. The CO 2 exchange resistance at air-water interface which could limit the photosynthesis was experimentally measured. It allowed the calculation of the free dissolved CO 2 concentration. The response to light showed a small O 2 uptake (37% of net photosynthesis in standard conditions) compared to C 3 plants; it was always higher than dark respiration and probably included a photoindependent part. The response to CO 2 showed: (a) an O 2 uptake relatively insensitive to CO 2 concentration and not completely inhibited with high CO 2, (b) a general inhibition of gas exchanges below 130 microliters CO 2 per liter (gas phase), (c) an absence of an inverse relationship between O 2 and CO 2 uptakes, and (d) a low apparent Km of photosynthesis for free CO 2 (1 micromolar). These results suggest that O 2 uptake in the light is the sum of different oxidation processes such as the glycolate pathway, the Mehler reaction, and mitochondrial respiration. The high affinity for CO 2 is discussed in relation to the use of HCO 3− and/or the internal CO 2 accumulation. 相似文献
13.
Responses of plants exposed to drought and rewatering have been well documented; however, little is known concerning strategies of psammophyte to drought and rewatering under different soil nutrient regimes. For this study, Pennisetum centrasiaticum under two soil nutrient regimes was subjected to progressive drought and subsequent rewatering. Soil water status, gas exchange characteristics, chlorophyll a fluorescence characteristics as well as biomass traits were measured to investigate ecophysiological responses. Net photosynthesis rate ( P n), stomatal conductance ( g s), water use efficiency, maximum quantum efficiency of photosynthesis system II (PSII, F V/ F M), electron transport flux per cross section (ET 0/CS 0), and performance index on cross section basis (PI CS) were suppressed during drought periods for both nutrient regimes. Meanwhile, leaf intercellular CO 2 concentration ( C i ), minimal fluorescence intensity ( F 0), and dissipated energy flux per cross section (DI 0/CS 0) increased. Reversible downregulation of PSII photochemistry and enhanced thermal dissipation of excess excitation energy (DI 0/CS 0) contributed to enhanced photo-protection in drought-stressed plants. Thus, the results indicate that P. centrasiaticum is capable of withstanding and surviving extreme drought events, and the recovery pattern of stressed P. centrasiaticum under both nutrient regimes was similar. However, fertilization increased the biomass and the variation in gas exchange and chlorophyll a fluorescence characteristics during drought periods. Additionally, fertilization accelerated the process of drought and aggravated stress under extreme drought events. Thus, the fertilization strategy used in P. centrasiaticum restoration should be carefully selected—fertilization may not always be beneficial. 相似文献
14.
Salicylic acid (SA) is a potent signaling molecule in plants and is involved in eliciting specific responses to biotic and abiotic stresses. The aim of this study is to investigate whether the exogenous application of SA can improve cadmium (Cd) induced inhibition of photosynthesis in castor bean ( Ricinus communis L.) plants. The effects of SA and Cd on plant growth, spectral reflectance, pigment contents, chlorophyll fluorescence and gas exchange were examined in a hydroponic cultivation system. Results indicate that Cd exposure significantly decreased the dry biomass, photosynthetic rate (P n), stomatal conductance (G s), intercellular CO 2 concentration (C i), pigment contents, quantum yield of PS II photochemistry (F v/F m), and effective quantum yield of PS II (??PS II) in the plants. Pretreatment with SA alone reduced the biomass and P n in castor bean plants, whereas pigment contents, F v/F m and ??PS II remained unaffected. Reduced G s, C i and E, as well as increased stomatal limitation (L s) and water use efficiency (WUE), were observed in plants pretreated with 500???M SA alone, whereas plants treated with 250???M SA were unaffected. Under Cd stress, SA pretreatment led to a significant decrease in P n, G s, E, C i, and chlorophyll contents (Chl a, Chl b, Chl a+b, Car, Chl a/b), and an increase in L s and WUE. Cd exposure enhanced spectral reflectance in the range 550?C680?nm and 750?C1,050?nm. It also decreased the normalized difference vegetation index ( chlNDI), the modified red edge simple ratio index (mSR 705), the red edge position (REP), water band index, and red/green ratio, whereas the structure independent pigment index (SIPI) was increased. Significant correlations ( P?<?0.01) between spectral indices (mSR 705, chlNDI, REP, red/green ratio) and pigment contents. SA significantly worsened plant growth and photosynthesis in Cd-stressed castor bean plants, in which a stomatal limitation was involved. The leaf spectral reflectance is a sensitive indicator in determining Cd toxicity in plants. 相似文献
15.
Plants of Zea mays were grown with different concentrations of nitrate (0.6, 4, 12, and 24 millimolar) and phosphate (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.12, 0.5, and 2 millimoles per square meter per second), and ambient partial pressures of CO 2 (305 and 610 microbars). Differences in mineral nutrition and irradiance led to a large variation in rate of CO 2 assimilation per unit leaf area ( A, 11 to 58 micromoles per square meter per second) when measured under standard conditions. The variation was shown, with the plants that had received different amounts of nitrate, to be related to variations in the nitrogen and chlorophyll contents, and phosphoenolpyruvate and ribulose-1,5-bisphosphate carboxylase activities per unit leaf area. Irrespective of growth treatment, A and leaf conductance to CO 2 transfer ( g), measured under standard conditions were in almost constant proportion, implying that intercellular partial pressure of CO 2 ( pi), was almost constant at 95 microbars. The same proportionality was maintained as A and g increased in an initially nitrogen-deficient plant that had been supplied with abundant nitrate. It was shown that pi measured at a given ambient partial pressure was not affected by the ambient partial pressure at which the plants had been grown, although it was different when measured at different ambient partial pressures. This suggests that the close coupling between A and g in these experiments is not associated with sensitivity of stomata to change in pi. Similar, though less comprehensive, experiments were done with Gossypium hirsutum, and yielded similar conclusions, except that the proportionality between A and g at normal ambient partial pressure of CO2 implied Pi ≈ 200 microbars. 相似文献
16.
The chemiluminescence reaction of lucigenin (Luc 2+?2NO 3?, N, N′‐dimethyl‐9,9′‐biacridinium dinitrate) at gold electrodes in dioxygen‐saturated alkaline aqueous solutions (pH 10) was investigated in detail by the use of electrochemical emission spectroscopy. We noted that both O 2 and Luc 2+ are reduced on a gold electrode in aqueous solution of pH 10 in almost the same potential region. From this fact, we expected chemiluminescence based on a radical–radical coupling reaction of superoxide ion (O 2· ?) and one‐electron reduced form of Luc 2+ (Luc· +, a radical cation). Chemiluminescence was actually observed in the potential range where O 2 and Luc 2+ were simultaneously reduced at the electrodes. The effects were examined upon addition of enzymes, i.e. superoxide dismutase (SOD) and catalase, into the solution and the substitution of heavy water (D 2O) for light water (H 2O) as a solvent on the chemiluminescence. In the presence of native and active SOD, chemiluminescence was completely absent. On the other hand, chemiluminescence was observed, unchanged in the presence of either denatured and inert SOD or catalase. In addition, the amount of chemiluminescence in D 2O solution was about three times greater than that in H 2O solution. These results, together with cyclic voltammetric results, suggest that O 2· ? participates directly in the chemiluminescence but H 2O 2 does not, and the chemiluminescence results from the coupling reaction between O 2· ? and Luc ·+ under the present experimental conditions. These chemically unstable species, O 2· ? and Luc· +, are produced during the simultaneous electroreduction of O 2 and Luc 2+. The coupling reaction between those radical species would lead to the formation of a dioxetane‐type intermediate and, finally, to chemiluminescence. The chemiluminescence reaction mechanism is discussed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
17.
The regulation of plant hydraulic conductance and gas conductance involves a number of different morphological, physiological and molecular mechanisms working in harmony. At the molecular level, aquaporins play a key role in the transport of water, as well as CO 2, through cell membranes. Yet, their tissue-related function, which controls whole-plant gas exchange and water relations, is less understood. In this study, we examined the tissue-specific effects of the stress-induced tobacco Aquaporin1 ( NtAQP1), which functions as both a water and CO 2 channel, on whole-plant behavior. In tobacco and tomato plants, constitutive overexpression of NtAQP1 increased net photosynthesis ( A N), mesophyll CO 2 conductance ( g m) and stomatal conductance ( g s) and, under stress, increased root hydraulic conductivity ( L pr) as well. Our results revealed that NtAQP1 that is specifically expressed in the mesophyll tissue plays an important role in increasing both A N and g m. Moreover, targeting NtAQP1 expression to the cells of the vascular envelope significantly improved the plants’ stress response. Surprisingly, NtAQP1 expression in the guard cells did not have a significant effect under any of the tested conditions. The tissue-specific involvement of NtAQP1 in hydraulic and gas conductance via the interaction between the vasculature and the stomata is discussed. 相似文献
18.
The dynamics of leaf photosynthesis in fluctuating light affects carbon gain by plants. Mesophyll conductance ( gm) limits CO 2 assimilation rate ( A) under the steady state, but the extent of this limitation under non-steady-state conditions is unknown. In the present study, we aimed to characterize the dynamics of gm and the limitations to A imposed by gas diffusional and biochemical processes under fluctuating light. The induction responses of A, stomatal conductance ( gs), gm, and the maximum rate of RuBP carboxylation ( Vcmax) or electron transport ( J) were investigated in Arabidopsis ( Arabidopsis thaliana (L.)) and tobacco ( Nicotiana tabacum L.). We first characterized gm induction after a change from darkness to light. Each limitation to A imposed by gm, gs and Vcmax or J was significant during induction, indicating that gas diffusional and biochemical processes limit photosynthesis. Initially, gs imposed the greatest limitation to A, showing the slowest response under high light after long and short periods of darkness, assuming RuBP-carboxylation limitation. However, if RuBP-regeneration limitation was assumed, then J imposed the greatest limitation. gm did not vary much following short interruptions to light. The limitation to A imposed by gm was the smallest of all the limitations for most of the induction phase. This suggests that altering induction kinetics of mesophyll conductance would have little impact on A following a change in light. To enhance the carbon gain by plants under naturally dynamic light environments, attention should therefore be focused on faster stomatal opening or activation of electron transport.Gas diffusional and biochemical processes impose significant limitations to CO2 assimilation during photosynthetic induction. 相似文献
19.
Chemiluminescence generated with the reaction of bis(2,4,6-trichlorophenyl)oxalate and hydrogen peroxide was applied to a detection system for high-performance liquid chromatography to determine fluorescamine-labeled catecholamines. The sensitivity of the chemiluminescence detection system with 25 fmol of detection limit was approximately 20 times higher than that of a conventional fluorescence detection system. Norepinephrine and dopamine in human urine were determined by the use of the new high-performance liquid chromatography detection system with the coefficient of variation of less than 4.0%. Good correlations ( r = 0.998 for norepinephrine and r = 0.999 for dopamine) were obtained between the values by the present method and the conventional method. 相似文献
20.
Experiments were performed to test the hypothesis that succulents “shift” their method of photosynthetic metabolism in response to environmental change. Our data showed that there were at least three different responses of succulents to plant water status. When plant water status of Portulacaria afra (L.) Jacq. was lowered either by withholding water or by irrigating with 2% NaCl, a change from C 3-photosynthesis to Crassulacean acid metabolism (CAM) occurred. Fluctuation of titratable acidity and nocturnal CO 2 uptake was induced in the stressed plants. Stressed Peperomia obtusifolia A. Dietr. plants showed a change from C 3-photosynthesis to internal cycling of CO 2. Acid fluctuation commenced in response to stress but exogenous CO 2 uptake did not occur. Zygocactus truncatus Haworth plants showed a pattern of acid fluctuation and nocturnal CO 2 uptake typical of CAM even when well irrigated. The cacti converted from CAM to an internal CO 2 cycle similar to Peperomia when plants were water-stressed. Reverse phase gas exchange in succulents results in low water loss to carbon gain. Water is conserved and low levels of metabolic activity are maintained during drought periods by complete stomatal closure and continual fluctuation of organic acids. 相似文献
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